This invention relates to polyamines and to compositions produced by the reaction of the polyamines with epoxy resins.
Certain aromatic polyamines are known for use as hardening agents for epoxy resins. However, coatings obtained from the reaction between these polyamines and epoxy resins, especially aromatic epoxy resins, often yellow with age, rendering them of limited usefulness.
Polyamines have now been discovered that can be reacted with nonaromatic epoxy resins, i.e. epoxy resins based on aliphatic or cycloaliphatic polyols to form coatings having a high resistance to yellowing with age and with exposure to ultraviolet radiation.
The polyamines of the invention are the reaction products of
A) at least one nonaromatic diamine containing from 2 to 40 carbon atoms, wherein the amine groups are primary amine groups; and
B) at least one epihalohydrin of the formula 
xe2x80x83where R is hydrogen or methyl and X is chlorine or bromine; wherein the mole ratio of component A) to component B) is about 2:1.
Other than in the operating examples, or where otherwise indicated, all numbers expressing quantities of ingredients or reaction conditions used herein are to be understood as modified in all instances by the term xe2x80x9caboutxe2x80x9d.
The polyamines of the invention, which are the reaction products of components A) and B) given above, preferably have the formula 
wherein R is hydrogen or methyl, and Rxe2x80x2 is a C2-40 aliphatic, cycloaliphatic, aliphatic cycloaliphatic, or polyoxyalkylene group, wherein the first three of these groups can optionally contain one or more nonconjucated double bonds. However, other nonaromatic diamines can also be used in the practice of the invention.
Examples of the nonaromatic diamines of component A) include, but are not limited to, the following: 1,3-bis(aminomethyl)cyclohexane, ethylenediamine, diethylenetriamine, triethylenetetramine, hexamethylenediamine, 2-methyl-1,5-pentanediamine-, 1,6-hexamethylenediamine, 2-heptyl-3,4-bis(9-aminononyl)-1-pentylcyclohexane(dimeryldiamine), polyoxyalkylene diamine, e.g. polyoxypropylene diamine, isophoronediamine, norbornodiamine, 2.5(2.6)-bis(aminomethyl)bicyclo(2.2.1) heptane, 4,4xe2x80x2-dicyclohexylmethane diamine, 1,4-diaminocyclohexane, menthanediamine, and bis(aminomethyl)cyclohexane.
Preferred nonaromatic diamines include those based on (i.e. containing) straight or branched chain saturated aliphatic groups, and those based on at least one cycloaliphatic group, optionally containing one or more nonconjugated double bonds.
Component B) is preferably epichlorohydrin, although epibromohydrin, 2-methyl epichlorohydrin, and 2-methyl epibromohydrin can also be used as component B).
The reaction between about 2 moles (e.g. from 2 to 2.1 moles) of component A) and one mole of component B) can be carried out by slowly adding component B) to component A) under a nitrogen atmosphere at a temperature in the range of from 200 to 100xc2x0 C., preferably from 23 xc2x0 to 60xc2x0 C. with stirring. After completion of the addition, from 0.5 to 1 mole of alkali metal hydroxide, preferably sodium hydroxide (a 50% aqueous solution for example) is added slowly with stirring. After this addition the mixture is heated to a temperature in the range of 650xc2x0 to 95xc2x0 C. for a period of several hours. The reaction mixture is then filtered to remove insoluble salts, and the reaction product isolated from the filtrate, e.g. by the removal of volatile components therefrom using vacuum distillation.
The polyamine of formula I can then be reacted with a nonaromatic epoxy resin at ambient temperatures to produce the coatings of the invention. The nonaromatic epoxy resin is based on an aliphatic or cycloaliphatic polyol, e.g. the polyglycidyl ether of polyether polyol, cycloaliphatic diepoxides, diglycidyl ether of hydrogenated Bis-phenol A, and the like.
The polyamine of formula I can be mixed with the nonaromatic epoxy resin in various proportions to form the coatings of the invention. However, weight ratios of (0.25 to 0.60):1 (polyamine:epoxy resin) are most suitable.
The coatings of the invention are light-stable and are accordingly very useful for outdoor applications. The coatings resist yellowing even after long periods of time exposed to daylight, which of course contains significant quantities of ultraviolet light.